1. Field of Invention
This application relates in general to two-stage trigger systems with improved safety and manufacturability features for semi-automatic weapons and specifically to the use of said trigger assembly on an AR-15 type rifle.
2. Prior Art
The trigger assembly of the proposed invention was designed to increase the control an individual shooter has over the timing of the host firearms discharge of a round and thereby effectively increase the accuracy potential of a shooter by minimizing mechanical distractions which hinder accurate gun fire. A smooth crisp trigger is essential if the user is to control when the firearm discharges. Precision shooters, be they military, law enforcement or civilian competitors require total control of the trigger mechanism to attain the maximum accuracy potential of their rifle. For military and law enforcement precision shooters control over the trigger mechanism is essential to the success of their respective missions.
Under optimal conditions a shooter wants to use as little force as is necessary to discharge his firearm. By minimizing the force necessary to manipulate the trigger group and thereby discharge the firearm the potential for pulling the firearm off target while manipulating the trigger is dramatically reduced. Lightening the trigger is an obvious solution to solving trigger related accuracy problems but concerns over safety must also be considered. Reducing the trigger pull weight also presents the potential for accidental or negligent discharges which can result in the loss of life, which is of particular concern to law enforcement and military end users.
Two stage triggers, which are well known in the prior art, allow for a smooth first stage and a light, crisp second stage which results in the firearm being discharged after the resistance is overcome. Two-stage triggers address many of the safety concerns which are present with light weight single stage triggers. Unfortunately many existing designs require the adjustment of set screws and/or the reduction of spring tension necessary to operate the hammer component of the trigger assembly. Set screws such as those found in U.S. Pat. No. 6,131,324 (Arnold W. Jewell) have a tendency to become threadedly unsecured after prolonged use. This often leads to a situation where the trigger either allows the uncontrolled discharge of the host weapon or prohibits the weapons from firing at all, this presents an obvious safety problem and concern for the user of a firearm equipped with such a trigger. A design which provides a smooth, crisp, and controlled trigger pull without the need of set screws if highly desirable. The design disclosed in this document requires no set screws to adjust the trigger pull weight and incorporates several safety features to prevent negligent discharge of the firearm.
Designs such as Rock River Arms two stage trigger rely on similar trigger disconnector geometry as found on factory AR15 or M16 triggers. These designs have a flat surface to surface contact which in the case of a pivoting component contacting another stationary component a flat surface to surface contact is extremely difficult to achieve as any deviation from perfect component size will in fact cause the two surfaces to not sit flat to each other thereby negatively affecting the primary sear engagement thus affecting the trigger pull weight. Any inconsistency between these two flat surfaces will dramatically and negatively affect the trigger mechanism as a whole. By providing a non linear surface with a partial radius on the trigger a line contact between the flat face of the disconnector and the partial radius on the trigger is provided, not a flat surface to flat surface contact. An another embodiment of the design could place the radius onto the disconnector face with the trigger surface being flat, the end result would be the same. With a flat surface contacting a cylindrical surface any differences in component size or position from ‘perfect’ will still allow the intended line contact at a point near where intended. This is a key aspect to providing a production two stage trigger which has a consistent, reliable trigger pull between each article of manufacture without the need of adjustable set screws or hand fitting.
While other designs such as those disclosed in U.S. Pat. No. 6,131,324 (Arnold W. Jewell) and U.S. Pat. No. 5,501,134 (Milazzo) require the adjustment of problematic set screws to adjust trigger pull weight the novel design described herein has incorporated another solution. Through the use of calibrated disconnector springs the trigger pull weight may be lowered or increased. This change in no way affects the reliability or safety of the trigger. While designs such a disclosed in U.S. Pat. No. 5,501,134 (Milazzo) do offer lighter disconnector springs, adjusting the set screws is still necessary to ensure proper function of such designs.
A safety sear similar to the primary sear present on the factory M16 or AR15 trigger group is also present. Many available triggers on the market do not have a secondary safety sear which would prevent the firearm from discharging should the primary sear break. This is of particular concern if the firearm is loaded and the firing mechanism is in the operational or “cocked” position. My design has incorporated a safety sear which will catch the hammer and prevent the weapon from discharging even if the primary sear brakes.
The present invention greatly reduces the probability of accidental firearm discharge while at the same time providing the user of a firearm appropriately equipped with desired trigger action characteristics. Shot to shot consistency of pull weight and travel is insured without abnormal manipulation or motion between shots.
Another improvement over other two stage triggers is the use of a precision sheet metal fabrication for the disconnector. The original M16 disconnector is manufactured by fineblanking which is a sheet metal stamping operation that will produce a part to close tolerances and fine surface finish on the edges of the part. Current two stage triggers that locate the primary sear above the trigger pin use investment castings or machined from solid metal disconnectors. Investment casings and machined disconnectors usually cost more per piece than an equivalent fineblanked or laser cut disconnector that is made from sheet metal. A sheet metal disconnector that is carried in the conventional M16 manner can be made to properly interface with a select-fire M16 safety selector so that a two stage trigger capable of fully automatic fire may be easily designed. The current invention carries a sheet metal disconnector in a trough that is located in the trigger in a manner similar to the original M16 disconnector. However, where the original M16 disconnector is located in an open trough whereas the current invention covers over part of the trough with a structure that carries the two stage trigger primary sear. This structure has an aperture or void that allows the disconnector to pass through the structure so that the disconnector stop may be located forward of the trigger pin.